This invention relates to devices providing indications of dynamic force. More particularly, this invention relates to instrumentation for measuring the dynamic force imparted by water/air spray on a landing craft air cushion (LCAC) during high-speed transit over the water.
High speed transit over water by LCACs exposes superstructure and equipment on deck to high-velocity sprays of water in the relatively fast moving air-stream. The forces created by the impacting air and water-spray acting on materials and equipment on deck can tear lines and other securing mechanisms apart, and the unsecured or loose materials and equipment can be swept over the side, can injure crewmembers, and cause significant damage to the LCAC.
If the forces created by the water/air spray could be determined or predicted under a variety of conditions, then sufficient means for securing the equipment stored on-deck could be installed and design criteria would be available for further equipment or modifications to existing equipment. However, there are no prior known methods to measure the dynamic impact of a water/air spray because there has been no way to determine the relative percentages of the two densities. Prior studies regarding loading on an underway LCAC assumed the loading created by wind only, and the studies did not take into account the fact that a significant majority of the dynamically impacting flow was comprised of water which has a density around 1,000 times that of air. When a soft-topped vehicle such as an LCAC is hit with 50 to 100 mph spray, the percentage of water content plays a significant part in the loading experienced by the structure and is too great to be ignored.
Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for instrumentation for measuring the dynamic force imparted by water/air spray on an LCAC during high-speed transit over the water.